From 848bd9acdcd00c164b42b14aacec242949ecd471 Mon Sep 17 00:00:00 2001 From: Gao Xiang Date: Sat, 8 Dec 2018 00:19:12 +0800 Subject: [PATCH] staging: erofs: fix use-after-free of on-stack `z_erofs_vle_unzip_io' The root cause is the race as follows: Thread #0 Thread #1 z_erofs_vle_unzip_kickoff z_erofs_submit_and_unzip struct z_erofs_vle_unzip_io io[] atomic_add_return() wait_event() [end of function] wake_up() Fix it by taking the waitqueue lock between atomic_add_return and wake_up to close such the race. kernel message: Unable to handle kernel paging request at virtual address 97f7052caa1303dc ... Workqueue: kverityd verity_work task: ffffffe32bcb8000 task.stack: ffffffe3298a0000 PC is at __wake_up_common+0x48/0xa8 LR is at __wake_up+0x3c/0x58 ... Call trace: ... [] __wake_up_common+0x48/0xa8 [] __wake_up+0x3c/0x58 [] z_erofs_vle_unzip_kickoff+0x40/0x64 [] z_erofs_vle_read_endio+0x94/0x134 [] bio_endio+0xe4/0xf8 [] dec_pending+0x134/0x32c [] clone_endio+0x90/0xf4 [] bio_endio+0xe4/0xf8 [] verity_work+0x210/0x368 [] process_one_work+0x188/0x4b4 [] worker_thread+0x140/0x458 [] kthread+0xec/0x108 [] ret_from_fork+0x10/0x1c Code: d1006273 54000260 f9400804 b9400019 (b85fc081) ---[ end trace be9dde154f677cd1 ]--- Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Signed-off-by: Greg Kroah-Hartman --- drivers/staging/erofs/unzip_vle.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c index f5d088fdf7f2..4404ea6fb9e4 100644 --- a/drivers/staging/erofs/unzip_vle.c +++ b/drivers/staging/erofs/unzip_vle.c @@ -744,13 +744,18 @@ static void z_erofs_vle_unzip_kickoff(void *ptr, int bios) struct z_erofs_vle_unzip_io *io = tagptr_unfold_ptr(t); bool background = tagptr_unfold_tags(t); - if (atomic_add_return(bios, &io->pending_bios)) + if (!background) { + unsigned long flags; + + spin_lock_irqsave(&io->u.wait.lock, flags); + if (!atomic_add_return(bios, &io->pending_bios)) + wake_up_locked(&io->u.wait); + spin_unlock_irqrestore(&io->u.wait.lock, flags); return; + } - if (background) + if (!atomic_add_return(bios, &io->pending_bios)) queue_work(z_erofs_workqueue, &io->u.work); - else - wake_up(&io->u.wait); } static inline void z_erofs_vle_read_endio(struct bio *bio) -- 2.30.2